JP2014048620A5 - - Google Patents

Description

However, when the method described in Patent Document 1 is applied in a low illuminance environment, an extremely large white balance coefficient is multiplied to a color signal having a minimal signal intensity. As a result, the noise component superposed on the original signal will be unnecessarily amplified, thus causing image deterioration.

In order to achieve the above object, a focus adjusting apparatus according to the present invention receives an image pickup optical system having a focus optical system for adjusting a focus state of a subject image, and the subject image via the image pickup optical system, the subject image is a focusing device for use in an imaging apparatus having an imaging device that outputs an image signal corresponding to each color signal is color-separated by a plurality of color filters, the detection and the signal intensity for each color signal a signal strength detecting means for, when all of the signal strength of each color signal detected by the signal intensity detecting means is equal to or greater than a predetermined threshold value, the luminance signal is multiplied by a coefficient corresponding to the signal strength of the respective color signals into color signals generate said at least one if it is less than the predetermined threshold value, the luminance signal generation hands to generate the luminance signal is multiplied by a predetermined constant factor to the color signals of the signal strength of each color signal And an AF evaluation value calculation means for extracting a predetermined frequency component from the luminance signal as a specific frequency component and calculating an AF evaluation value according to the specific frequency component, and driving control of the focus optical system along the optical axis. and while, by detecting the position of the focus optical system in which the AF evaluation value becomes maximum as the maximum position, and shifted by a predetermined amount determined by the characteristics of the imaging optical system in accordance with the signal intensity of the respective color signals from the maximum position And a control means for driving and controlling the focus optical system at the in- focus position with the position as the in-focus position .

The control method according to the present invention includes an imaging optical system having a focus optical system for adjusting a focus state of a subject image, the subject image received via the imaging optical system, and the subject image having a plurality of colors. a method of controlling a focusing device for use in an imaging apparatus having an imaging device that outputs an image signal corresponding to the color signals subjected to color separation by the signal intensity detecting step of detecting the signal intensity for the color signals When all of the signal strength of the signal strength detection color signals detected in step is equal to or higher than the predetermined threshold value, and generates a luminance signal by multiplying a coefficient which the corresponding to the signal strength of each color signal to color signals, each color When at least one of signal strength of the signal is less than the predetermined threshold value, a luminance signal generation step of generating the luminance signal is multiplied by a predetermined constant factor to each color signal, before Extracted as specific frequency components in a predetermined frequency component from the luminance signal, the AF evaluation value calculating step of calculating the AF evaluation value in accordance with the specific frequency component, while driving and controlling the focusing optics along the optical axis, The position of the focus optical system at which the AF evaluation value is maximized is detected as a maximum position, and a position shifted from the maximum position by a predetermined amount determined by the characteristics of the imaging optical system according to the signal intensity of each color signal is combined. And a control step of driving and controlling the focus optical system at the in-focus position as a focus position .

A control program according to the present invention includes an imaging optical system having a focus optical system for adjusting a focus state of a subject image, the subject image received through the imaging optical system, and the subject image having a plurality of color filters. a is the control program used -system in focusing device of an image pickup apparatus having an imaging device that outputs an image signal corresponding to the color signals subjected to color separation by the focusing device comprises a computer, wherein for each color signal a signal intensity detecting step of detecting the signal intensity, the signal intensity when all of the signal strength of each color signal detected by the detecting step is equal to or greater than a predetermined threshold value, the coefficient of each color signal corresponding to the signal intensity of the color signals generating a luminance signal by multiplying the said at least one if it is less than the predetermined threshold, the respective color signals by a predetermined constant coefficient signal strength of each color signal A luminance signal generating step of multiplying to generate the luminance signal; an AF evaluation value calculating step of extracting a predetermined frequency component from the luminance signal as a specific frequency component and calculating an AF evaluation value according to the specific frequency component; while driving and controlling the focusing optics along an optical axis, wherein to detect the position of the focus optical system AF evaluation value becomes maximum as the maximum position, corresponding to the signal intensity of the respective color signals from the maximum position And a control step of driving and controlling the focus optical system at the in- focus position with a position shifted by a predetermined amount determined by the characteristics of the imaging optical system as the in-focus position .

It is a block diagram which shows an example of an imaging device provided with the focus adjustment apparatus by the 1st Embodiment of this invention. 3 is a flowchart for explaining processing (focus position detection processing) when detecting a focus position of a focus lens performed by the imaging apparatus shown in FIG. 1. 2A and 2B are diagrams for explaining the image sensor shown in FIG. 1, in which FIG. 1A is a diagram illustrating a pixel array, and FIG. 2B is a diagram illustrating a basic block unit ; It is a figure which shows the color space when the horizontal axis is the color evaluation value Cx and the vertical axis is the color evaluation value Cy. It is a flowchart for demonstrating the process performed by the signal strength detection part and luminance signal processing part which are shown in FIG. It is a figure which shows an example of the relationship between a focus lens position and AF evaluation value at the time of acquiring AF evaluation value using BPF, driving-controlling a focus lens. It is a figure which shows an example of the relationship between a subject's spatial frequency and a color component, and BP correction amount. It is a block diagram which shows an example of an imaging device provided with the focus adjustment apparatus by the 2nd Embodiment of this invention. It is a flowchart for demonstrating the process performed by the signal strength detection part and luminance signal processing part which are shown in FIG.

The AF control unit 108 refers to the focus correction amount (BP correction amount) corresponding to the AF evaluation value and the signal amplification coefficient set according to the signal intensity of each color, and the position of the focus lens 102 in the in-focus state (BP correction amount). Find the focus position. The AF control unit 108 controls driving of the focus lens 102 along the optical axis based on the in-focus position.

The CPU 104 determines whether or not the shutter button has been half-pressed (SW1 ON) (step S101). If SW1 is OFF (NO in step S101), the CPU 104 stands by. On the other hand, the user starts photographing, to the press the shutter button halfway (in Step S101, YES), CPU 104 starts the focus position detecting process.

First, when the focus lens 102 is at the position P1, the CPU 104 calculates an AF evaluation value according to the pixel signal obtained in the imaging state by the imaging optical system 101 (step S102). That is, the AF evaluation value calculation processing unit 107 extracts the specific frequency component from the luminance signal obtained from the pixel signal when the focus lens 102 is at the position P1, and obtains the AF evaluation value (the AF evaluation value is obtained as the AF evaluation value). P1).

If n = M (YES in step S107), the AF control unit 108 determines whether or not a predetermined peak value exists based on the AF evaluation value Pn (step S109). If it is determined that there is a predetermined peak value ( YES in step S109), the AF control unit 108 obtains a position Pp at which the AF evaluation value is a maximum value, and adds a BP correction amount to the position Pp to obtain a position Pf. Then, the AF control unit 108 drives and controls the focus lens 102 to the position Pf (step S110). In calculating the position Pp, a known interpolation calculation is used.

Thereafter, the CPU 104 determines whether or not the shutter button is fully pressed (SW2 ON), which is a main photographing instruction ( step S111). If SW2 is OFF (NO in step S111), the CPU 104 stands by.

FIG. 3 is a diagram for explaining the image sensor 103 shown in FIG. 1. FIG. 3A is a diagram showing a pixel arrangement, and FIG . 3B is a diagram showing a basic block unit .

The signal intensity detection unit 105 calculates color evaluation values Cx, Cy, and Yi based on the following formulas (1) to (3) for each of these basic block units (hereinafter also referred to as basic blots) . However, R, G1, G2, and B represent outputs in each pixel.

First, the signal intensity detection unit 105 determines whether or not all of the average values IR, IG1, IG2, and IB of the pixel signal intensity for each color are smaller than a threshold value Ith that defines the low luminance of the subject (step S201 ). . When all of average values IR, IG1, IG2, and IB are smaller than threshold value Ith (if it is less than the threshold value: YES in step S201), signal intensity detecting unit 105 calls all the white balance coefficients, Replace with AveWB (average value of white balance coefficient of each color) which is a constant coefficient. Here, AveWB is an average value of the white balance coefficients kWB_R, kWB_G1, kWB_G2, and kWB_B.

In particular, in the case of low illuminance or the like, this tendency becomes prominent when the intensity of each color signal, which is the output of the image sensor 103 , decreases. In order to increase the AF speed, it is necessary to increase the readout rate of the image sensor 103 and shorten the image signal acquisition time when calculating the AF evaluation value. Therefore, when signals are read out from the image sensor 103, pixel addition processing may be performed to reduce the number of read pixels and shorten the signal read time of the image sensor 103.

That is, a low-intensity signal is amplified so as to complement the intensity difference between the color signals that are the output of the image sensor, and the focus position is corrected by a predetermined amount. In this case, a predetermined BP correction amount may be prepared for each focal length and photographing distance that accompanies the zooming of the optical system.

PAF = (2 × PGL + PBL + PRL) ÷ 4 (13)

BP correction amount = PCapt−PAF = [2 × (PGH−PGL) + (PBH−PBL) + (PRH−PRL)] ÷ 4 (15)
Since the BP correction amount shown in Expression (15) is a weighted average of the correction amounts (PGH-PGL) , (PBH-PBL) , and (PRH-PRL) for each color, this amount can be calculated from the design value or The BP correction amount can be obtained by measuring the difference in imaging position in the case corresponding to AF and photographing using the same white balance coefficient at the time of manufacture.

First, the signal intensity detection unit 105 determines whether or not the subject luminance value BV1 measured by the photometry unit 111 is smaller than the first threshold value BVth1 of the luminance value that defines the low luminance of the subject (step S301). When the subject luminance value BV1 ≧ the first threshold value BVth1 (first threshold value or more: NO in step S301), the signal intensity detection unit 105 determines that the subject luminance value BV1 is the second luminance value that defines the low luminance of the subject. It is determined whether it is smaller than the threshold value BVth2 (step S302). Note that the first threshold BVth1 <the second threshold BVth2.

On the other hand, if it is determined that the subject luminance value BV1 <the first threshold value BVth1 (less than the first threshold value: YES in step S301), the luminance signal processing unit 106 determines that all of the signal intensity detection unit 105 has calculated Recalls the white balance coefficient. Then, the luminance signal processing unit 106 replaces the white balance coefficient with AveWB, which is a predetermined constant coefficient (step S303). Here, AveWB is an average value of the white balance coefficients kWB_R, kWB_G1, kWB_G2, and kWB_B of each color. That is, the luminance signal processing unit 106 sets white balance (WB) coefficient = average value.

When the subject luminance value BV1 <the second threshold value BVth2 (less than the second threshold value: YES in step S303), the luminance signal processing unit 106 determines the white balance coefficients kWB_R, kWB_G1, and kWB_G2 for each color according to the subject luminance value BV1. , And an intermediate value between kWB_B and an average value thereof (step S304).

Thus, in the second embodiment of the present invention, use in accordance with the photometry result of the photometry section 111, all of the white balance coefficient, the average value, and any of the average value and the intermediate value between the white balance coefficient To determine. When the pixel signal is weak due to low illuminance, the white balance coefficient is not multiplied. Thereby, it is possible to prevent amplification of random noise components such as standing noise and shot noise caused by dark current included in a weak pixel signal.

Claims (8)

An imaging optical system having a focus optical system for adjusting the in-focus state of the subject image, and each color signal obtained by receiving the subject image via the imaging optical system and color-separating the subject image by a plurality of color filters A focus adjustment device used in an imaging device having an imaging device that outputs an image signal according to
A signal strength detecting means for detecting the signal intensity for each color signal,
When all of the signal strength of each color signal detected by the signal intensity detecting means is equal to or greater than a predetermined threshold value, and generates a luminance signal by multiplying a coefficient corresponding to the signal intensity of the color signals to the color signals, the color signals When at least one of the signal strength is below the predetermined threshold value, the luminance signal generation means for generating the luminance signal is multiplied by a predetermined constant factor to each color signal,
AF evaluation value calculating means for extracting a predetermined frequency component from the luminance signal as a specific frequency component and calculating an AF evaluation value according to the specific frequency component;
While driving and controlling the focusing optics along an optical axis, wherein to detect the position of the focus optical system AF evaluation value becomes maximum as the maximum position, corresponding to the signal intensity of the respective color signals from the maximum position Control means for driving and controlling the focus optical system at the in- focus position, with the position shifted by a predetermined amount determined by the characteristics of the imaging optical system as the in-focus position ;
A focus adjustment device comprising: Furthermore, a photometric means for detecting the luminance of the subject and obtaining a photometric result is provided,
The luminance signal generating means uses the photometric result instead of the signal intensity of each color signal to determine the predetermined constant coefficient when the subject luminance value indicated by the photometric result is less than a predetermined first threshold value. The focus adjustment apparatus according to claim 1, wherein the luminance signal is generated by multiplying a signal. The luminance signal generation means is configured such that when the subject luminance value is equal to or greater than the predetermined first threshold value and the subject luminance value is equal to or greater than a second threshold value that is greater than the predetermined first threshold value, The focus adjustment apparatus according to claim 2, wherein a luminance signal is generated by multiplying each color signal by a coefficient corresponding to the signal intensity of each color signal. The luminance signal generation means, when the subject luminance value is greater than or equal to the predetermined first threshold and the subject luminance value is less than the second threshold, the constant coefficient and the signal intensity of each color signal 4. The focus adjustment apparatus according to claim 3, wherein a luminance signal is generated by obtaining an intermediate value with a coefficient corresponding to the color value and multiplying each color signal by the intermediate value.   The focus adjustment apparatus according to claim 1, wherein the coefficient is a coefficient used for adjusting white balance of an image. Wherein the predetermined shift amount which is determined by the characteristics of the imaging optical system in the color signals, seeking a predetermined amount shifted by shifting position determined by the characteristics of the imaging optical system in accordance with the signal intensity of the color signals, said control means focusing device according to any one of claims 1 to 5, characterized in that said focusing optics the alloy only shifting position the shifting position focus position from the maximum position. An imaging optical system having a focus optical system for adjusting the in-focus state of the subject image, and each color signal obtained by receiving the subject image via the imaging optical system and color-separating the subject image by a plurality of color filters A method of controlling a focus adjustment device used in an imaging device having an imaging device that outputs an image signal according to
A signal intensity detecting step of detecting the signal intensity for each color signal,
When all of the signal strength of the signal strength detection color signals detected in step is equal to or higher than the predetermined threshold value, and generates a luminance signal by multiplying a coefficient corresponding to the signal intensity of the color signals to the color signals, the color signals When at least one of the signal strength is below the predetermined threshold value, a luminance signal generation step of generating the luminance signal is multiplied by a predetermined constant factor to each color signal,
An AF evaluation value calculating step of extracting a predetermined frequency component from the luminance signal as a specific frequency component and calculating an AF evaluation value according to the specific frequency component;
While driving and controlling the focusing optics along an optical axis, wherein to detect the position of the focus optical system AF evaluation value becomes maximum as the maximum position, corresponding to the signal intensity of the respective color signals from the maximum position A control step of driving and controlling the focus optical system at the in- focus position, with the position shifted by a predetermined amount determined by the characteristics of the imaging optical system as the in-focus position ;
A control method characterized by comprising: An imaging optical system having a focus optical system for adjusting the in-focus state of the subject image, and each color signal obtained by receiving the subject image via the imaging optical system and color-separating the subject image by a plurality of color filters A control program used in a focus adjustment device of an imaging device having an image sensor that outputs an image signal according to
A computer included in the focus adjustment device,
A signal intensity detecting step of detecting the signal intensity for each color signal,
When all of the signal strength of the signal strength detection color signals detected in step is equal to or higher than the predetermined threshold value, and generates a luminance signal by multiplying a coefficient corresponding to the signal intensity of the color signals to the color signals, the color signals When at least one of the signal strength is below the predetermined threshold value, a luminance signal generation step of generating the luminance signal is multiplied by a predetermined constant factor to each color signal,
An AF evaluation value calculating step of extracting a predetermined frequency component from the luminance signal as a specific frequency component and calculating an AF evaluation value according to the specific frequency component;
While driving and controlling the focusing optics along an optical axis, wherein to detect the position of the focus optical system AF evaluation value becomes maximum as the maximum position, corresponding to the signal intensity of the respective color signals from the maximum position A control step of driving and controlling the focus optical system at the in- focus position, with the position shifted by a predetermined amount determined by the characteristics of the imaging optical system as the in-focus position ;
A control program characterized by causing